improved method for demagnetisation of naval vessels and preisach analysis
DESCRIPTION
Improved method for demagnetisation of naval vessels and Preisach analysis. T. M. Baynes, G. J. Russell and A. Bailey University of New South Wales, Sydney Australia Maritime Operations Division D.S.T.O. Australia. Demagnetisation. (from Chikazumi 1967). Anhysteretic magnetisation. Z Coil. - PowerPoint PPT PresentationTRANSCRIPT
Improved method for demagnetisation of naval
vessels and Preisach analysis
T. M. Baynes, G. J. Russell and A. BaileyUniversity of New South Wales, Sydney AustraliaMaritime Operations Division D.S.T.O. Australia
-1
0
1
-2000 -1000 0 1000 2000H (A/m)
M/Ms
major hysteresisloop
anhysteretic
initial curve
Demagnetisation
(from Chikazumi 1967)
Anhysteretic magnetisation
X Coil
Z Coil
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1 Stage 2 Stage 3
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1 Stage 2
3 Stage Deperm
-2000
-1000
0
1000
2000
0 150 300 450
Time (mins)
Ap
plied
Fie
ld (
A/m
) Stage 1
Deperm on Submarine
-1
0
1
0 35 70
Shot Number
Longitudin
al M
-1.5
0
1.5
Vert
ical M
submarine long.submarine vert.
-1
0
1
0 35 70
Shot Number
Longitudin
al M
submarine long.
Problems with Flash D
1.Redundancy
2.Time consuming
3.Predicting deperm outcome
Anhsyteretic Deperm
-2000
-1000
0
1000
2000
0 450
Time
Ap
plied
Fie
ld
(A/m
)
Longitudinal magnetisation during deperm
-1
0
1
0 35 70
Shot Number
M lo
ngitudin
al
submarine long.tube long.
-1
0
1
0 35 70
Shot Number
Longitudin
al M
submarine long.
0
0.001
-10000 -5000 0 5000 10000Deviation from average final LM (A/m)
Norm
ali
sed
fin
al
LM
data
200 A/m100 A/m40 A/m25 A/m3 Stage
0
0.001
-10000 -5000 0 5000 10000Deviation from average final LM (A/m)
Norm
ali
sed
fin
al
LM
data
200 A/m100 A/m40 A/m25 A/m
Final LM
012345
0 50 100Number of Steps
(
kA
/m)
Final VM
0
50
100
150
200
250
0 50 100Number of Steps
(
A/m
)
Distribution of Results
0
0.01
-400 -200 0 200 400Deviation from average VM (A/m)
No
rmalised
data
fo
r fi
nal V
M
200 A/m Steps100 A/m Steps40 A/m steps25 A/m3 Stage Deperm
Anhysteretic deperm results
Preisach Model
-1
0
1
-1 0 1
H/Hmax
M/M
max
bn
bn+1
bn+2
MR (H1 , H2 ) = f(-H1 ).f(H2 )
MR initial(H) =1/2 f(H) 2
0
10
20
30
40
50
60
0 500 1000 1500 2000 2500H (A/m)
MR (
kA
/m)
Stage 1 data approximation
0
10
20
30
40
50
60
0 500 1000 1500 2000 2500H (A/m)
MR (
kA/m
)
Initial R emanent M C urve
0
10
20
30
40
50
60
0 500 1000 1500 2000 2500H (A/m)
MR (
kA/m
)
Initial R emanent M C urveAnhysteretic deperm on tube
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
0 5 10 15 20 25
Shot number
M/M
sta
rttheorytube
Stage 1 Data for submarine
-1.2
-0.8
-0.4
0
0.4
0.8
1.2
0 5 10 15
Shot number
M /
Msta
rtsubmarinetheory
Remanent VM after anhysteretic deperm
0
3000
0 200 400 600 800
Vertical Bias Field (A/m)
Rem
an
en
t V
M
(A/m
)
Conclusions:• laboratory simulation allows experiments into
alternative deperm procedures.• Anhysteretic deperm produces more reliable
vertical magnetisation AND allows for theoretical modelling. Flash D can not be modelled easily.
• Preisach model used to describe bulk magnetisation changes in tube.
• It’s possible to use just use the initial remanent magnetisation curve to predict deperm results.
• Stage 1 data from previous deperms on submarines can be used as approximation for initial curve – can also predict deperm results.
-10000
-5000
0
5000
10000
15000
-1 0 1x (m)
M (nT)
tube alone
-10000
-5000
0
5000
10000
15000
-1 0 1x (m)
M (nT)
tube alone
-10000
-5000
0
5000
10000
15000
-1 0 1x (m)
M (nT)
block alone
-10000
-5000
0
5000
10000
15000
-1 -0.5 0 0.5 1x (m)
M (nT)
combined
-10000
-5000
0
5000
10000
15000
-1 0 1x (m)
M (nT)
block alone
-10000
-5000
0
5000
10000
15000
-1 -0.5 0 0.5 1x (m)
M (nT)
combined